/*
 * This file contains code from "C++ Primer, Fourth Edition", by Stanley B.
 * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the
 * copyright and warranty notices given in that book:
 *
 * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo."
 *
 *
 * "The authors and publisher have taken care in the preparation of this book,
 * but make no expressed or implied warranty of any kind and assume no
 * responsibility for errors or omissions. No liability is assumed for
 * incidental or consequential damages in connection with or arising out of the
 * use of the information or programs contained herein."
 *
 * Permission is granted for this code to be used for educational purposes in
 * association with the book, given proper citation if and when posted or
 * reproduced.Any commercial use of this code requires the explicit written
 * permission of the publisher, Addison-Wesley Professional, a division of
 * Pearson Education, Inc. Send your request for permission, stating clearly
 * what code you would like to use, and in what specific way, to the following
 * address:
 *
 *  Pearson Education, Inc.
 *  Rights and Contracts Department
 *  75 Arlington Street, Suite 300
 *  Boston, MA 02216
 *  Fax: (617) 848-7047
*/

#include <exception>
#include <stdexcept>

void handle_out_of_memory(const std::bad_alloc&) { }

template <class T> class Handle
{
public:
Handle(T* p = 0) try :
		ptr(p), use(new size_t(1))
	{
	} catch (const std::bad_alloc& e)
	{
		handle_out_of_memory(e);
	}

	// overloaded operators to support pointer behavior
	T& operator*();
	T* operator->();
	const T& operator*() const;
	const T* operator->() const;

	// copy control: normal pointer aliasing; but last Handle deletes the object
	Handle(const Handle& h): ptr(h.ptr), use(h.use)
	{
		++*use;
	}
	Handle& operator=(const Handle&);
	~Handle()
	{
		rem_ref();
	}
private:
	T* ptr;
	size_t* use;
	void rem_ref()
	{
		if (--*use == 0) {
			delete ptr;
			delete use;
		}
	}
};

/*  workaround: MS Compiler doesn't support out of line definition
 *  of function try block for template class constructor
template <class T> Handle<T>::Handle(T *p)
try : ptr(p), use(new size_t(1))
{
     // empty function body
}  catch(const std::bad_alloc &e)
       { handle_out_of_memory(e); }
*/

template <class T>
inline
Handle<T>& Handle<T>::operator=(const Handle& rhs)
{
	++*rhs.use;
	rem_ref();     // decrement use count and delete pointers if needed
	ptr = rhs.ptr;
	use = rhs.use;
	return *this;
}

template <class T> inline T& Handle<T>::operator*()
{
	if (ptr) return *ptr;
	else throw std::runtime_error
		("derference of unbound Handle");
}
template <class T> inline T* Handle<T>::operator->()
{
	if (ptr) return ptr;
	else throw std::runtime_error
		("access through unbound Handle");

}

template <class T> inline
const T& Handle<T>::operator*() const
{
	if (ptr) return *ptr;
	else throw std::runtime_error("derference of unbound Handle");
}
template <class T> inline
const T* Handle<T>::operator->() const
{
	if (ptr) return ptr;
	else throw std::runtime_error("access through unbound Handle");

}
